I've done a fair amount of mixes after the fact for Playing Dead. Eventually I learned that, for the most part, less is more when it comes to effects and compression. I use Logic Pro. I am a total amateur at it.
I use stereo busses (buses?) for everything -- drums, vocals, bass, instruments, which allows me to adjust the overall balance between everything without having to mess with 12 different drum faders, or three vocal faders. I use some soft limiting on the master to get the overall track gain up at the end.
For me the busses are the key ... if your individual channels are running fairly hot, like they should be, maybe peaks around -3, you run out of headroom in a hurry on the overall mix. The busses let me control everything easily.
I usually pan the piano hard one way, rhythm guitar hard the other way, lead guitar slightly off center, vocals with a very slight spread, and pan one drummer left and one drummer right, with a spread on the toms, kicks and snares pretty hard panned, overheads hard panned. Use stereo to open up the soundscape.
I will typically find a track in the middle of the set, and get the basic mix where I want it, then set the automated faders so I can listen through the set, and bring up levels on the instruments as needed here and there ... boost the keyboards during a solo, that sort of thing. My band generally stays pretty consistent all night long, so I'm not riding a lot of faders, just here and there.
This is a set opener with 16 tracks, a Jack Straw. https://soundcloud.com/vicderobertis/01jackstraw
If you are using the same board every night, then it's pretty easy to just to make a basic template with your mix more or less set up with panning, EQ, etc., then just drop the new tracks on there for a starting point. We usually are using the same mics every night, so I don't have to start from scratch with the kick drum every mix, I can generally get the whole thing sounding pretty good in a couple of hours. Then I give my ears a nice break and go back and listen again.
Post up some samples and ask for critiques. It's good to pick a nice Dead soundboard to listen to right before you mix, too, it sets your ears. One of my go-to recordings is "Candyman" from the first set of the Shoreline 10-4-87. That's a beautiful Healy mix.